<!doctype html>
<html lang="en">
 <head>
  <meta charset="UTF-8">
  <meta name="Generator" content="EditPlus®">
  <meta name="Author" content="">
  <meta name="Keywords" content="">
  <meta name="Description" content="">
  <title>哈哈</title>
	<!--我就是要把JS写在这里,让页面元素加载完后再执行JS代码-->
	<script>
		window.onload = function(){
		









			var oBox = document.getElementById('box');
			oBox.style.background = 'green';












		};	
	</script>
 </head>
 <body>
		<div id="box" style="width:100px; height:100px; background:red;">哈哈</div>
 </body>
</html>

